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07 November 2011 <br /> AGE-NC Project No. 00-0769 <br /> Page 6 of 7 <br /> other wells. <br /> • During the fourth quarter 2011, 1,2-DCA concentrations increased from non-detect <br /> in well MW-3B and decreased in samples collected from MW-2B, MW-4D, MW-4E, <br /> and MW-5A compared to the previous sampling event. <br /> • During the fourth quarter 2011, TAME concentrations increased in samples <br /> collected from wells MW-1, MW-3B (increased from non-detect), and MW-613 and <br /> decreased in samples collected from wells MW-213, MW-3A (decreased to non- <br /> detect), MW-4 (A-E), and MW-5 (B-E) compared to the previous sampling event. <br /> 1,2-DCA and TAME concentrations remained generally stable in all other wells. <br /> • The lateral and vertical extent of petroleum hydrocarbon-impacted ground water <br /> remains somewhat undefined; however the dissolved plume has been assessed. <br /> The volume of the dissolved plume has been documented with grab ground water <br /> samples and monitoring well samples. <br /> • Additional sources of adsorbed or dissolved contamination are possible based on <br /> the distance the dissolved plume has laterally migrated. <br /> 5.0. RECOMMENDATIONS <br /> Based on the results of this and previous investigations, AGE recommends: <br /> • Continuation of the-semi-annual ground water monitoring and reporting program; <br /> --the-next-gro er monitoring event will be scheduled for April 2011. <br /> • DiscontinuationoftheSVEs stem operation until groundwater elevations decrease <br /> and allow-for recharge of the impacted soil vapor exposed to the extraction well <br /> network. <br /> • Evaluation of alternative dissolved hydrocarbon remediation technologies (in-situ <br /> air injection or in-situ in-well air sparging) when remediation operation resumes. <br /> Advanced GeoEnvironmental,Inc. <br />